﻿/************************************************************************

   Extended Silverlight Toolkit

   Copyright (C) 2010-2012 Xceed Software Inc.

   This program is provided to you under the terms of the Microsoft Public
   License (Ms-PL) as published at http://extendedsilverlight.codeplex.com/license

   Please purchase a commercial version of this toolkit if you are using
   it in a commercial product. The commercial versions support the project,
   and also include more features for each control, priority support,
   source code, updates, removed watermark, and a proprietary license.

   Visit http://xceed.com and follow @datagrid on Twitter.

  **********************************************************************/

using System;
using System.ComponentModel;
using System.Linq.Expressions;
using Xceed.Silverlight.DataGrid.Utils;

namespace Xceed.Silverlight.DataGrid
{
  internal abstract class ViewModelBase : INotifyPropertyChanged
  {
    #region Constructor

    protected ViewModelBase()
    {
      m_propertyChangedHelper = new NotifyPropertyChangedHelper( this, this.RaisePropertyChangedEvent );
    }

    #endregion

    #region IsCleared Protected Property

    protected bool IsCleared
    {
      get
      {
        return m_isCleared;
      }
    }

    private bool m_isCleared;

    #endregion

    protected virtual void PreInitialize()
    {
    }

    protected virtual void OnInitialize()
    {
    }

    protected virtual void PostInitialize()
    {
    }

    protected virtual void PreClear()
    {
    }

    protected virtual void OnClear()
    {
    }

    protected virtual void PostClear()
    {
    }

    internal void Initialize()
    {
      if( m_isInitializing.IsSet )
        return;

      using( m_isInitializing.Set() )
      {
        this.PreInitialize();
        this.OnInitialize();
        this.PostInitialize();
      }
    }

    internal void Clear()
    {
      if( this.IsCleared || m_isClearing.IsSet )
        return;

      using( m_isClearing.Set() )
      {
        try
        {
          this.PreClear();
          this.OnClear();
          this.PostClear();
        }
        finally
        {
          m_propertyChangedHandler = null;
          m_isCleared = true;
        }
      }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged
    {
      add
      {
        if( this.IsCleared )
          return;

        m_propertyChangedHandler += value;
      }
      remove
      {
        if( this.IsCleared )
          return;

        m_propertyChangedHandler -= value;
      }
    }

    protected void RaisePropertyChanged<TMember>( Expression<Func<TMember>> expression )
    {
      m_propertyChangedHelper.RaisePropertyChanged( expression );
    }

    private void RaisePropertyChangedEvent( string propertyName )
    {
      if( m_propertyChangedHandler != null )
      {
        m_propertyChangedHandler.Invoke( this, new PropertyChangedEventArgs( propertyName ) );
      }
    }

    private readonly NotifyPropertyChangedHelper m_propertyChangedHelper;
    private PropertyChangedEventHandler m_propertyChangedHandler;

    #endregion

    #region Private Fields

    private readonly InhibitorFlag m_isInitializing = new InhibitorFlag();
    private readonly InhibitorFlag m_isClearing = new InhibitorFlag();

    #endregion
  }
}
